With development of the wireless broadband networks and mobile communication technologies, users have now been accustomed to use of various mobile apparatuses in dealing with different matters such as in working, communication or entertainment. For conventional wireless communication systems, data and control signals necessary for wireless communication between user equipments (UEs) must all be processed by a base station and a core network, and this will cause the problem of core network congestion in the conventional wireless communication systems. Correspondingly, the concept of device-to-device (D2D) communication has been proposed to cope with this problem. The D2D communication means that a UE can directly communicate with a target device without a base station or an access point (AP). As compared to the conventional way in which the UEs must communicate via a base station, the D2D communication has the advantages of reducing the transmission power, decreasing the transmission delay and improving the spatial reuse efficiency.
Unlike the conventional D2D communication technologies such as Bluetooth, Wireless Fidelity (Wi-Fi) or the like, the new generation of D2D communication technologies (e.g., the LTE D2D communication technology proposed by the 3rd Generation Partnership Project (3GPP) Long Term Evolution/Long Term Evolution-Advanced (LTE/LTE-A)) attracts more and more attention because they can search for neighboring devices within a large range quickly by use of a legally authorized frequency spectrum and allow for direct communication under the control and assistance of the base station. Nevertheless, the new generation of D2D communication technologies are still confronted with various problems and challenges.
For example, the new generation of D2D communication technologies are implemented on the basis of the existing wireless communication architecture, so they have to share the pre-existing wireless frequency spectrum resources with the existing wireless communication systems. However, the conventional D2D communication technologies are only able to select UEs intended to perform D2D communication according to a single selection procedure (or a single selection parameter), so it is difficult to find out a UE that actually needs to communicate. Therefore, if the new generation of D2D communication technologies are only able to select a UE according to a single procedure, waste of the pre-existing wireless frequency spectrum resources will be caused. Accordingly, an urgent need exists in the art to provide an effective D2D communication selection technology for the new generation of D2D communication technologies.